Performance attributes for memory

ABSTRACT

An example device in accordance with an aspect of the present disclosure includes a plurality of memory segments corresponding to at least one memory channel of a computing system that is to receive a memory module. A performance attribute of an Advanced Configuration and Power Interface (ACPI) table is set to indicate performance of at least one of the plurality of memory segments, and is usable for memory allocation by an operating system memory manager.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/420,313, which was filed on Jan. 31, 2017, which is herein includedby reference in its entirety for all purposes.

BACKGROUND

In computing systems, such as servers, the number of memory channels ofcentral processing units (CPUs/processors) continues to increase.Populating the memory channels with balanced memory configurations, suchas by using the same type of memory module (e.g., dual inline memorymodule (DIMM) to fully populate the memory channels), can reduce thelikelihood of poor memory performance. However, fully populating thememory channels can result in unnecessarily exceeding application needs,while negatively affecting server power consumption and total systemcosts. Although a computing system can support imbalanced memoryconfigurations (in terms of physical memory population, technologies,and capacities) to alleviate excessive power consumption and systemcosts, such imbalanced configurations introduce performance bottlenecksin memory subsystems and increased complexity in operating systems andapplications, resulting in performance degradation.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1 is a block diagram of a computing system including at least oneperformance attribute according to an example.

FIG. 2 is a block diagram of a computing system including performanceattribute establishing instructions, notification identificationinstructions, and memory allocation instructions according to anexample.

FIG. 3 is a block diagram of a computing system including memorychannels associated with different bandwidth performance, and at leastone performance attribute according to an example.

FIG. 4 is a block diagram of a computing system including memorychannels associated with different power efficiency performance, and atleast one performance attribute according to an example.

FIG. 5 is a flow chart based on establishing at least one performanceattribute according to an example.

FIG. 6 is a flow chart based on ordering memory segments, generating anotification, and consolidating memory contents according to an example.

DETAILED DESCRIPTION

Computing systems can obtain, via attributes, some information abouttheir installed memory configuration or memory sub-system designtopology. However, attributes currently defined by the AdvancedConfiguration and Power Interface (ACPI) Hardware Specification Standardprovide little information about installed memory configuration ormemory sub-system design topology (such as the memory topology dictatedby chassis mechanical form-factor constraints). Without suchinformation, the computing system (e.g., an operating system (OS) memorymanager) may randomly allocate memory into computing system regionshaving limited bandwidth, which can result in reduced performance (e.g.,up to 20% performance degradation) for memory-intensive workloads. Inaddition, the OS memory manager has no guidance for utilizing memoryregions efficiently for additional power saving opportunities.

To address such issues, examples described herein may provide attributesthat can be utilized (e.g., by an OS memory manager) for enhanced memoryallocation and to minimize system performance impact even for imbalancedmemory configurations. In example implementations, such attributes canbe presented through firmware, through an ACPI table, and the like. Byusing attributes to support such imbalanced physical memory topologyconfigurations, example implementations can address drawbacks identifiedabove, by enabling the computing system to optimize physical memoryallocations and access patterns, among other optimizations. In thismanner, examples described herein may enable flexibility for serverconfigurations/pricing strategies, enabling right-sized memoryconfigurations targeted for various workloads. An OS memory manager canuse such example attributes to enhance the memory allocation process andto minimize system performance impacts associated with imbalanced memoryconfigurations. Furthermore, the attributes can be used to consolidatesystem memory for better power efficiency using memory power domains,e.g., when the computing system is not running at full capacity.

FIG. 1 is a block diagram of a computing system 100 including at leastone performance attribute 112 according to an example. The computingsystem 100 also includes a plurality of memory segments 107,corresponding to at least one memory module associated with at least onememory channel 105. A non-transitory machine-readable storage medium 104is encoded with instructions executable by the computing system 100that, when executed, cause the computing system to establish theperformance attribute 112 as part of an Advanced Configuration and PowerInterface (ACPI) Hardware Specification table (ACPI table) 110. Theperformance attribute 112 can be set to indicate the performance of atleast one of the plurality of memory segments 107. The performanceattribute 112 also is usable for memory allocation by an operatingsystem memory manager (not shown in FIG. 1; see FIG. 3).

The ACPI specification generally enables a computing system to discoverand configure hardware components, such as by performing statusmonitoring and putting unused components to sleep. Thus, the exampleimplementations described herein can use the ACPI specification as amechanism to enable a given computing system platform to communicate toan OS. However, other techniques can be used to communicate theinformation of the performance attributes 112, such as through the useof a platform intercept.

The performance attributes 112 are shown located in the ACPI table 110,which can be stored in computing system firmware. The firmware can takethe performance attributes 112 and write them to a memory locationreadable by the computing system OS. Firmware instructions can beexecuted by a computing system at bootup, before an OS has been loaded,and can remain active after the OS has been loaded. Firmwareinstructions for example can be executed by basic input/output system(BIOS) of the computing system. Higher level instructions, such asSystem OS instructions, can be loaded in memory of the computing systemupon bootup, and executed during normal operation of the computingsystem after bootup. Higher level instructions can rely on the OS toprovide abstraction of various computing resources, such as access tovirtual memory. In an example implementation, the computing system 100can boot up under direction of the firmware, which discovers thecomputing system topology including what type of memory (e.g., DIMMs)and its configuration. Based on such information, the system firmwareformulates the ACPI table 110 and makes such information available(e.g., to the OS), based on the framework including the exampleperformance attributes 112. The non-transitory machine-readable storagemedium 104 can be encoded as firmware instructions of the computingsystem 100.

The performance attributes 112 can be presented in terms of memorysegmentation. A performance attribute 112 can specify that a givensegmentation (memory segment 107) has a given size, a given bandwidthperformance, a given power efficiency performance, or other type ofperformance.

The example implementations of the ACPI table 110 can be provided as anACPI table that is updated to include the performance attributes 112. Inalternate example implementations, the ACPI table 110 can be provided asa newly created table. The ACPI table 110 can be updated to reflectvarious use cases, such as hard adding or removing memory, which maylikely result in different memory segmentation having different behaviorthan before.

In contrast to existing ACPI attributes, such as system localitydistance information table (SLIT) attributes, the example performanceattributes 112 can provide information such as the memory interleavingscheme and the partition of the memory segmentation behind the memorycontroller, which enable optimization and allocation of memory to theappropriate application and thread. Furthermore, unlike the existingACPI attributes, the example performance attributes 112 enable memoryconsolidation as well as sizes of different memory segmentation anddifferent bandwidths. Accordingly, the performance attributes 112 enableadditional features, e.g., enable an OS to assign the most frequent andlargest dataset to a largest memory bank width, for enhancedperformance, as well as enable the OS to consolidate memory contentsinto regions of power efficient memory, reducing power usage of thecomputing system without negative performance implications.

Performance attributes 112 indicate memory range and type, and areusable by the OS memory manager, or a hypervisor, or other component ofthe computing system 100 to optimize memory management (e.g., enablingbetter performance and power efficiency). The performance attributes 112can be interpreted by ACPI components of the OS, such as by the OSloader and/or within the OS initialization, to be passed to the OSmemory manager to customize memory handling based on the performanceattributes 112.

The population of memory in the computing system 100 is flexible, e.g.,additional memory channels 105 may be added, which results in thepossibility of diverse memory segmentation. By using the performanceattributes 112, the computing system 100 can allocate memory to enhanceperformance, thereby avoiding allocating memory to region(s) that wouldworsen system performance. The performance attributes 112 enable a moreintelligent use of memory by, e.g., the OS memory manager, to allocatememory segments 107 to specifically optimize for a given workload,including power efficiency and performance optimizations.

In an example implementation, the performance attribute 112 indicatesbandwidth performance, e.g., bandwidth performance associated with aphysical configuration of a memory module(s) that is to populate thememory channel(s). In an example implementation, the performanceattribute 112 is to indicate a power efficiency. The performanceattribute 112 also can correspond to a memory subsystem design topologycorresponding to a mechanical form factor of the computing system 100.Such performance attributes, relating to power efficiency and/orbandwidth performance, can be used by the OS memory manager toconsolidate system memory for better power efficiency using memory powerdomains when the utilization of the computing system 100 can accommodatethe memory consolidation (e.g., when not fully saturated by a workload).In an example implementation, degrees of power efficiency (e.g., high,medium, low, and so on) can be determined based on relative powerefficiencies available in a given computing system. For example, acomputing system can have a first memory channel associated with fullpower usage, and a second memory channel associated with half the powerusage of the first memory channel. Accordingly, the first memory channelcan be deemed low power efficiency, and the second memory channel can bedeemed high power efficiency. Similarly, degrees of bandwidthperformance can be relatively established for a given computing system.

Memory modules can interface with memory channels 105 of the computingsystem 100. The performance attributes 112 can specify portions of thememory at a granularity of memory address segmentation, i.e., one ormore memory segments 107. Accordingly, the performance attributes canspecify different segments even within a given memory module, such as amemory module that is configurable into different operational modes(e.g., volatile storage, non-volatile random access, etc.). Exampleimplementations can define, based on the performance attributes 112, aphysical memory pool assignable to virtual memory according to dynamictuning and application physical memory needs. The memory channels 105 ofexample computing systems 100 can accommodate different types of memory,even simultaneously within the same computing system, includingremovable and on-die modules. The performance attributes 112 can be usedto accommodate such different types of memory, including differentsegments within such memory types. Different types of memory/segmentscan imply different usage scenarios, for use by the OS. Even a singlememory module can be defined as system memory, as block memory, as blockstorage, and/or as application memory. Accordingly, segmentation ariseseven if the memory is physically arranged symmetrically in the memorychannels 105 (e.g., fully and/or evenly populated). Despite such issues,the performance attributes 112 inform the OS how best to make use of thedifferent types of memory at a high degree of granularity, therebyenhancing performance and avoiding and need to make assumptions andsuffer performance degradation. Similar to segmentation issues regardingmemory types, segmentation can arise for different power efficienciesamong memory, even in a mostly or fully populated system. Accordingly,the performance attributes also can be used to improve system powerefficiency by intelligently utilizing memory segments that are powerefficient, regardless of a given physical memory configuration, whetherbalanced or unbalanced, and whether partially, mostly, or fullypopulated.

The computing system 100 can use a notification 116 to indicate a changein the performance attribute(s) 112, such as to indicate a change inmemory configuration of the computing system 100. In an exampleimplementation, the notification 116 can be provided in the form of abasic input/output system (BIOS) notification attached to the ACPI table110. The notification 116 informs the OS to reload the ACPI table(s) 110to check for changes. In an example, memory contents can be reallocatedinto different memory regions/segments 107. The notification 116 alsocan be used to inform the computing system 100 of a power optimizationfor the memory allocation, based on intelligently monitoring workloadusage for better results. The OS can then dynamically adjust the memoryallocation approach based on the corresponding notification 116. In someexample implementations, the notification 116 can take the form of anACPI notification or use other existing notification structures, such asa BIOS notification attached to the ACPI table 110. In an example usecase scenario, additional memory is added to the computing system 100 asits workload demands, and the computing system 100 (e.g., via firmwareand/or BIOS) can issue the notification 116 for the OS to reload thecorresponding new performance attributes 112 that were dynamicallypopulated into the ACPI table 110 by the system.

The computing system 100 can be based on disaggregated memory.Accordingly, a pool of memory can be dynamically added without affectingthe design of the computing system 100. Thus, the performance attributes112 and the notifications 116 can apply to the topology of the memorywithin the computing system 100, as well as to a pool(s) of memory addedexternal to the computing system 100. It is thus possible to keep trackof the memory topology, with performance attributes 112 that changedynamically as new memory is added and/or as old memory is removed fromthe computing system 100.

A memory controller (e.g., to perform the functionality of a memorymanager) is not shown in FIG. 1, and in some example implementations canbe included within the computing system 100 (e.g., internal). In somealternate implementations, the memory controller can be providedexternal to the computing system 100, e.g., as a memory controllerdisaggregated from the computing system 100. The performanceattribute(s) 112 are applicable regardless of the implementation of thememory controller.

Accordingly, the performance attributes 112 expose memory information tothe OS, enabling the OS to make informed decisions on memory allocationand thereby improving computing system performance and memory managerrobustness in bandwidth, power efficiency, and the like. The performanceattributes 112 enable memory allocation approaches that minimize anyperformance implications of imbalanced memory configurations, andimprove power efficiency during low workload demand periods. Theperformance attributes can be implemented in the ACPI table 110 toincrease OS memory manager robustness. The chance of system performancedegradation due to imbalanced memory configurations is minimized, andadditional power savings are enjoyed while satisfying datacenter demandsfor flexibility in offering computing systems having imbalanced memoryconfiguration at low cost, without performance trade-offs.

FIG. 2 is a block diagram of a computing system 200 includingperformance attribute establishing instructions 210, notificationidentification instructions 220, and memory allocation instructions 230according to an example. The computing system 200 also includes aprocessor 202, coupled to the computer-readable media 204 on whichinstructions 210-230 are stored. The computing system 200 is toestablish performance attributes 212, which may be stored in ACPI table210.

Computer-readable media 204 may be accessible by the system 200, toserve as a computer-readable repository to store information such asperformance attributes 212 that may be referenced by one or more enginescorresponding to instructions 210, 220, 230. As described herein, theterm “engine” may include electronic circuitry for implementingfunctionality consistent with disclosed example implementations, and maybe included in the computing system 100 of FIG. 1. For example, enginescan represent combinations of hardware devices (e.g., processor and/ormemory) and programming (e.g., processor-executable instructions210-230) to implement the functionality consistent with disclosedimplementations. An example system (e.g., a computing device), such ascomputing system 100, may include and/or receive the tangiblenon-transitory computer-readable media storing the set ofcomputer-readable instructions. As used herein, the processor/processingresource may include one or a plurality of processors, such as in aparallel processing system, to execute the processor-executableinstructions. The memory can include memory addressable by the processorfor execution of computer-readable instructions. The computer-readablemedia can include volatile and/or non-volatile memory such as a randomaccess memory (“RAM”), magnetic memory such as a hard disk, floppy disk,and/or tape memory, a solid state drive (“SSD”), flash memory, phasechange memory, and so on.

The performance attribute establishing instructions 210 are to establisha performance attribute of an ACPI table. The performance attributecorresponds to at least one of a plurality of memory segments of atleast one memory channel of a computing system that is to receive amemory module.

The notification identification instructions 220 are to identify anotification indicating a change in status of the computing system.

The memory allocation instructions 230 are to, in response to thenotification, allocate memory by an operating system memory manageraccording to the performance attribute.

FIG. 3 is a block diagram of a computing system 300 including memorychannels 305 associated with different bandwidth performance, and atleast one performance attribute 312 according to an example. Thecomputing system includes a plurality of CPUs 301, 302, to interact withthe memory channels 305. The memory channels 305 of the exampleimplementation of computing system 300 include high bandwidth memorychannel 321, and low bandwidth memory channel 322. The OS memory manager314 interacts with the CPUs 301, 302, and with the ACPI table 310. TheACPI table 310 includes the performance attributes 312, and the OSmemory manager 314 is to send and receive notifications 316.

The ACPI hardware specification table 310 (ACPI table) can be providedby updating an existing ACPI table to include new characteristics toaccommodate the example performance attributes 312. In alternateexamples, the ACPI table 310 can be provided as a new table compatiblewith ACPI standards, or other such approaches for communicatingperformance status information.

The notification 316 similarly can be provided as an update to theexisting ACPI notification structure, or by using other notificationstructures (e.g., hot-plug notifications) to communicate updates to theperformance attributes 312 to enable the computing system 300 todynamically respond to changes in memory configuration/operations. Thenotifications 316 enable the OS memory manager 314 to be alerted to ACPIcomponents, and allows identification of the presence of the ACPI table310, and to report the performance attributes 312.

The example computing system 300 is shown having memory channels 305 ofdifferent bandwidths, e.g., high bandwidth 312 such as a full bandwidthmemory channel, and low bandwidth 322 such as a half bandwidth memorychannel. Accordingly, the performance attributes 312 can include abandwidth performance attribute, to express information such as amaximum available bandwidth for a given memory segment, memory channel,populated DIMM configuration, server design topology, or other aspect ofthe computing system 300. The bandwidth performance attributes 312therefore enable the OS memory manager 314 to define physical memorypools based on the physical memory bandwidth, server topologyinformation, and/or memory physical regions provided by the bandwidthperformance attributes 312 and based on application requests. Thebandwidth performance attributes 312 and notifications 316 enable the OSmemory manager 314 to select the appropriate physical memory pool, anddynamically tune the virtual memory assignment to physical memorymapping based on memory accessing characteristics defined by theapplications' physical memory needs and via the OS's paging and swappingmechanism respecting the applications' workload needs. Thus, over time,the bandwidth performance attributes 312 enable policies for thisimbalanced memory configurations (e.g., having varying bandwidthperformance across available memory segments and/or memory channels 305)to allocate those processes, having large active data sets in virtualmemory, to physical memory locations associated with a high bandwidth321 performance attribute 312. Similarly, applications having smalleractive data sets can be allocated to regions associated with lowbandwidth 322 performance attributes 312, for imbalanced memoryconfigurations/topologies as illustrated in FIG. 3. Thus, by applyingthe bandwidth performance attributes 312, performance implicationsassociated with imbalanced memory configurations can be minimized.

The OS memory manager 314 can identify characteristics ofthreads/processes that are to make use of the memory, such as thebehavior a process based on its application, its data set size, howfrequently the process accesses memory, and so on. The OS memory manager314 can then use the bandwidth performance attributes 312 tointelligently and dynamically allocate the processes to memory byfitting the characteristics of the threads/processes to memory accordingto the bandwidth performance attributes 312. Thus, the performanceattributes 312 provide information to optimize and best fit the natureof the behavior and operation of threads/processes to available (e.g.,potentially imbalanced) memory for efficient performance. Such tuningcan be performed dynamically, and the OS memory manager 314 can treatthe performance attributes 312 as hints regarding consolidation ofmemory to achieve higher overall memory bandwidth and performance.

In example embodiments, the degree to which performance is prioritizedcan be customized, e.g., via user preferences. Thus, a user can set ahigher priority for power savings, and the OS memory manager 314 cantake into consideration whether to place a higher priority on maximizingbandwidth performance by using bandwidth performance attributes 312 toallocate memory, versus using other performance attributes (such aspower efficiency), depending on what characteristics a given topologymay exhibit (e.g., whether it has one or more imbalances in the memorysystem that can be optimized for).

FIG. 4 is a block diagram of a computing system 400 including memorychannels 405 associated with different power efficiency performance, andat least one performance attribute 412 according to an example. Similarto the example computing system 300 of FIG. 3, the computing system 400also includes a plurality of CPUs 401, 402, to interact with the memorychannels 405. The memory channels 405 include high power (e.g., “hot”)memory channel 423, medium power (e.g., “warm”) memory channel 424, andlow power (e.g., “cold”) memory channel 425. The OS memory manager 414interacts with the CPUs 401, 402, and with the ACPI table 410. The ACPItable 410 includes the performance attributes 412, and the OS memorymanager 414 is to send and receive notifications 416.

The OS memory manager 414 can use notifications 416 and performanceattributes 412 similar to the OS memory manager 314 described above withrespect to FIG. 3. Additionally, the performance attributes 412 canrepresent power efficiency performance attributes. Thus, the OS memorymanager 414 (and 314) can perform memory consolidation based on theperformance attributes 312, 412. Such power efficiency (and bandwidth)performance attributes 312, 412 can be provided in addition to otherattributes such as whether a given memory region is persistent orvolatile, enabling additional benefits regardless of whether a givenmemory region is persistent or volatile.

The OS memory managers 314, 414 also can perform consolidation when theworkload in a given memory segment/region is low, rather than performingconsolidation randomly within the system memory pool. Accordingly, byfocusing in memory segmentation(s) when demand is low, performance isnot negatively affected. Furthermore, by consolidating into, e.g., morepower efficient memory segments, the remaining segments can go unusedand put into a sleep mode to allow the computing system 400 to consumesignificantly less power. Such power efficiency improvements can berealized by use of the performance attributes 412 regardless of a givenphysical memory configuration, whether balanced or unbalanced, andwhether partially, mostly, or fully populated.

The power efficiency performance attributes 412 enable ordering ofphysical memory locations that can be utilized, e.g., based on afirst-to-allocate and last-to-use approach by the OS memory manager 414for improved power efficiency (e.g., in a computing system 400 having animbalanced memory topology regarding memory power efficiency). The powerefficiency performance attribute 412 (and/or the bandwidth performanceattribute 312) can be assigned (e.g., by system BIOS and/or firmware) toeach physical memory region, which can by at a higher granularity than asingle memory channel/memory module (e.g., different performanceattributes 312/412 can be assigned to different memory segments within agiven memory module/for a given memory channel).

A given memory segment associated with a memory channel 405 can bedesignated with a “hot,” “warm,” or “cold” power efficiency performanceattribute 412. The OS memory manager 414 can use the performanceattributes 412 to consolidate memory allocation to save power orincrease bandwidth, e.g., in the order of the memory classifications.For example, the “hot” region(s) can be allocated first, then “warm,”and lastly “cold.” Memory allocation or de-allocation sequences canreflect system workload demands, e.g., as requested by runningapplications. The memory chunk size of these regions can be varied andprogrammed by applying different memory interleaving schemes to thememory segment(s).

The performance attributes 412 enable additional power savings on top ofmemory sub-system power management features. The aggressiveness ofmemory consolidation can be associated with OS power management options,e.g., user selectable and configurable options. Use of a more aggressivepolicy can yield higher power savings but lower performance. Such tuningcan be performed dynamically, and the OS memory manager 414 can treatthe performance attributes 312, 412 as a hint for consolidating memory.Thus, when not needed, memory can be consolidated into smaller regionsto save power in particular, rather than by randomly allocating memory.

Referring to FIGS. 5 and 6, flow diagrams are illustrated in accordancewith various examples of the present disclosure. The flow diagramsrepresent processes that may be utilized in conjunction with varioussystems and devices as discussed with reference to the precedingfigures. While illustrated in a particular order, the disclosure is notintended to be so limited. Rather, it is expressly contemplated thatvarious processes may occur in different orders and/or simultaneouslywith other processes than those illustrated.

FIG. 5 is a flow chart 600 based on establishing at least oneperformance attribute according to an example. In block 510, aperformance attribute of an Advanced Configuration and Power Interface(ACPI) Hardware Specification table is established. The performanceattribute corresponds to at least one of a plurality of memory segmentscorresponding to at least one memory channel of a computing system thatis to receive a memory module. For example, computing system firmwarecan perform a discovery routine to identify available memory and itsassociated performance, and populate the ACPI table with correspondingperformance attributes to characterize the available memory that is tobe allocated. In block 520, memory is allocated by an operating systemmemory manager according to the performance attribute. The performanceattribute can indicate at least one of i) bandwidth performance, and ii)power efficiency. For example, the computing system can be deployed in apower-savings usage scenario, and accordingly prioritize allocatingmemory to power efficient segments of memory based on the powerefficiency performance attribute. During periods of low use, the examplecomputing system can further consolidate memory into the power efficientsegments, allowing unused segments to go into a sleep mode. In alternateexamples/usage scenarios, the computing system can optimize forperformance, based on the bandwidth performance attributes. Suchprioritization, whether for bandwidth performance or power efficiencyperformance, can be user-configurable for a given computing system.

FIG. 6 is a flow chart 600 based on ordering memory segments, generatinga notification, and consolidating memory contents according to anexample. In block 610, the plurality of memory segments are ordered,based on the performance attribute, according to a performance hierarchyfor a first-to-allocate and last-to-use approach. For example, thecomputing system can use the performance attributes to identify whichmemory segments are “hot,” and prioritize allocation of data to thosememory segments first. In block 620, a notification is generated inresponse to a change in workload usage. For example, the computingsystem can dynamically monitor for any changes in configuration ofmemory topology/installation, and update the performance attributesaccordingly, to reflect the memory performance at a high degree ofgranularity. The performance attributes for the memory segments can berearranged, based on physically adding/removing and/or moving memorymodules with respect to the available memory channels of the computingsystem. Furthermore, in example implementations, the data can bere-allocated in response to changes in application loads/needs placed onthe memory, independent of whether the memory topology has physicallychanged. In block 630, memory contents can be consolidated, in responseto a notification of low workload demand status, into at least onememory segment whose corresponding at least one performance attributethat indicates high power efficiency. For example, an OS memory managercan identify that applications have placing the memory in a low usagecondition, and consolidate memory contents into those memory segmentswhose performance attribute is “cold,” resulting in power savings notonly due to use of more power efficient memory for stored contents, byalso by consolidating and allowing any remaining unused memory segments(which may be cold, warm, and/or hot) to enter sleep mode.

Examples provided herein may be implemented in hardware, software, or acombination of both. Example systems can include a processor and memoryresources for executing instructions stored in a tangible non-transitorymedium (e.g., volatile memory, non-volatile memory, and/or computerreadable media). Non-transitory computer-readable medium can be tangibleand have computer-readable instructions stored thereon that areexecutable by a processor to implement examples according to the presentdisclosure.

An example system (e.g., including a controller and/or processor of acomputing device) can include and/or receive a tangible non-transitorycomputer-readable medium storing a set of computer-readable instructions(e.g., software, firmware, etc.) to execute the methods described aboveand below in the claims. For example, a system can execute instructionsto direct an allocation engine to allocate memory according to exampleperformance attributes, wherein the engine(s) include any combination ofhardware and/or software to execute the instructions described herein.As used herein, the processor can include one or a plurality ofprocessors such as in a parallel processing system. The memory caninclude memory addressable by the processor for execution of computerreadable instructions. The computer readable medium can include volatileand/or non-volatile memory such as a random access memory (“RAM”),magnetic memory such as a hard disk, floppy disk, and/or tape memory, asolid state drive (“SSD”), flash memory, phase change memory, and so on.

What is claimed is:
 1. A computing system comprising: a plurality ofmemory segments corresponding to at least one memory channel that is toreceive a memory module; and a non-transitory machine-readable storagemedium encoded with instructions executable by the computing systemthat, when executed, cause the computing system to: establish aperformance attribute of an Advanced Configuration and Power Interface(ACPI) Hardware Specification table, wherein the performance attributeis set to indicate a memory interleaving scheme of at least one of theplurality of memory segments, and is usable for memory allocation by anoperating system memory manager; load the ACPI table into operatingsystem memory; identify, by the operating system memory manager, acharacteristic of a process for which memory is to be allocated;allocate memory by the operating system memory manager according to theperformance attribute and according to the characteristic, wherein theperformance attribute indicates at least one of i) bandwidthperformance, and ii) power efficiency; identify a notification issued inresponse to a change in the performance attribute; in response to theidentified notification, reload the ACPI table with the changedperformance attribute into the operating system memory; and reallocatethe memory by the operating system memory manager according to thechanged performance attribute in the reloaded ACPI table and accordingto the characteristic.
 2. The computing system of claim 1, wherein thebandwidth performance is associated with a physical configuration of atleast one memory module that is to populate the at least one memorychannel.
 3. The computing system of claim 1, wherein the instructions,when executed, further cause the computing system to establish anadditional performance attribute of the ACPI Hardware Specificationtable, wherein the additional performance attribute is associated with amemory subsystem design topology corresponding to a mechanical formfactor of the computing system.
 4. The computing system of claim 1,wherein the non-transitory machine-readable storage medium is encoded asfirmware instructions of the computing system, wherein the firmwareinstructions direct the computing system to copy the performanceattribute from the ACPI table to a memory usable by an operating systemof the computing system.
 5. The computing system of claim 1, wherein theinstructions, when executed, further cause the computing system toestablish an additional performance attribute of the ACPI HardwareSpecification table, wherein the additional performance attribute isprovided at a granularity of memory address segmentation within a givenmemory module that is configurable into different operational modes. 6.The computing system of claim 1, wherein the instructions, whenexecuted, further cause the computing system to send a notification tothe operating system memory manager to indicate a change in theperformance attribute.
 7. A method, comprising: establishing aperformance attribute of an Advanced Configuration and Power Interface(ACPI) Hardware Specification table, wherein the performance attributecorresponds to at least one of a plurality of memory segmentscorresponding to at least one memory channel of a computing system thatis to receive a memory module; loading the ACPI table into operatingsystem memory; identifying, by an operating system memory manager, acharacteristic of a process for which memory is to be allocated;allocating memory by the operating system memory manager according tothe performance attribute and according to the characteristic, whereinthe performance attribute indicates at least one of i) bandwidthperformance, and ii) power efficiency; identifying a notification issuedin response to a change in the performance attribute; in response to theidentified notification, reloading the ACPI table with the changedperformance attribute into the operating system memory; and reallocatingthe memory by the operating system memory manager according to thechanged performance attribute in the reloaded ACPI table and accordingto the characteristic.
 8. The method of claim 7, further comprising:reallocating the memory according to a user preference that indicates anextent to which power savings is to be prioritized relative toperformance.
 9. The method of claim 7, further comprising: identifyinglow workload demand status of the computing system; and consolidatingmemory contents into at least one memory segment whose corresponding atleast one performance attribute that indicates high power efficiency.10. The method of claim 7, wherein the characteristic indicates a dataset size for the process.
 11. The method of claim 7, wherein thecharacteristic indicates a frequency at which the process accessesmemory.
 12. A non-transitory machine-readable storage medium encodedwith instructions executable by a computing system that, when executed,cause the computing system to: establish a performance attribute of anAdvanced Configuration and Power Interface (ACPI) Hardware Specificationtable, wherein the performance attribute corresponds to at least one ofa plurality of memory segments of at least one memory channel of acomputing system that is to receive a memory module, and wherein theperformance attribute is set to indicate a partition of a memorysegmentation behind a memory controller; load the ACPI table intooperating system memory, wherein an operating system memory managerperforms memory allocation according to the performance attribute in theloaded ACPI table; identify a notification issued in response to achange in the performance attribute; and in response to the identifiednotification, reload the ACPI table with the changed performanceattribute into the operating system memory, wherein the operating systemmemory manager re-performs memory allocation according to the changedperformance attribute in the reloaded ACPI table.
 13. The storage mediumof claim 12, wherein the notification is to indicate a change in memoryconfiguration of the computing system.
 14. The storage medium of claim12, wherein the computing system is to generate the notification inresponse to a change in the ACPI table.
 15. The storage medium of claim14, wherein the change in the ACPI table is based on physical change inthe at least one memory module installed in the computing system. 16.The storage medium of claim 14, wherein the change in the ACPI table isbased on a segmentation change in the at least one memory moduleinstalled in the computing system.
 17. The storage medium of claim 16,wherein the segmentation change is contained within a given one of theat least one memory module.
 18. The storage medium of claim 14, whereinthe change in the ACPI table is based on a change in memory populatingthe computing system.